Method of manufacturing a surgical model

ABSTRACT

A surgical model simulating certain aspects of the natural anatomical joint is made by first providing a male mould conforming externally to the general anatomy of an internal cavity of the joint. A coating of resilient impermeable penetrable material is applied over the male mould. The coating is removed from the male mould to form an open capsule. A closure is provided for the capsule attached to the open capsule so as to form an impermeable penetrable capsule, the capsule conforming internally to the general anatomy of the internal cavity of the joint and containing simulated joint components. The capsule is arranged within a mould, the mould being at least partly lined with a penetrable outer skin material, and the capsule is embedded in a penetrable packing material. Finally, the model is removed from the mould.

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a surgicalmodel and more particularly, but not exclusively, relates to a method ofmanufacturing a surgical model which simulates certain aspects of anatural anatomical joint and which is capable of being prepared withrealistic simulation of certain pathologies for demonstrating and/orpractising appropriate surgical techniques by arthroscopy in a realisticmanner using endoscopic surgical instruments.

Surgical models for demonstrating and/or practising surgical techniquesby arthroscopy are generally unrealistic. For example, existing modelsare often anatomically incorrect, at least insofar as the properties ofthe materials used for the models are concerned, are generally providedwith pre-formed portals and are generally not watertight. Theseshortcomings give rise to significant difficulties in the training ofsurgeons in arthroscopic techniques in which, for example, thepositioning of the portals and irrigation of the joint are particularlyimportant.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodof manufacturing a surgical model which eliminates or at least reducesthese deficiencies of prior art models.

According to the present invention there is provided a method ofmanufacturing a surgical model simulating certain aspects of the naturalanatomical joint, the method comprising the steps of: providing a malemould conforming externally to the general anatomy of an internal cavityof the joint; applying a coating of resilient impermeable penetrablematerial over the male mould; removing the coating from the male mouldto form an open capsule; providing a closure for the capsule andattaching the closure to the open capsule so as to form an impermeablepenetrable capsule, the capsule conforming internally to the generalanatomy of the internal cavity of the joint and containing simulatedjoint components; arranging the capsule within a mould, the mould beingat least partly lined with a penetrable outer skin material; embeddingthe capsule in a penetrable packing material; and removing the modelfrom the mould.

The method may include the step of reinforcing the model, for examplewith a fibrous, mesh or gauze material. The reinforcement may be appliedto the coating of resilient material and/or the skin.

The capsule may be filled with fluid such as water or saline, tosimulate synovial fluid, which fluid may be pressurised.

The skin of the model and the capsule may be formed of an elastomericcompound such as rubber, for example silicone rubber, or a colloidmaterial, for example based on gelatine.

The packing material may comprise light discrete particulate materialsuch as polystyrene beads or may comprise a moulded light material, forexample expanded polystyrene or polyurethane, or may comprise the samematerial as the skin and/or the capsule.

The closure for the capsule may comprise an articular surface of a boneforming part of the joint.

The method may include the step of passing an elongate member simulatinga ligament and/or a tendon through at least a part of the capsule,either before or after the closure is inserted. The elongate member maythen be secured externally of the capsule. The elongate member maycomprise an elastomeric material. The elongate member may incorporate aflexible elongate element extending from at least one end thereof. Theflexible elongate element may extend through the elongate member in theaxial direction thereof. The flexible elongate element may comprisestring or a like filamentary material.

The joint comprising the surgical model may be in the form of a kneestructure, the knee structure comprising femoral condyles with a femoralnotch therebetween, medial and lateral menisci, anterior and posteriorcruciate ligaments and tibial articular surfaces. The mould forreceiving the capsule may be an inverted knee-shape. The method mayinclude the step of arranging within the mould a simulated patellarcomplex positioned intermediate the capsule and the skin. The patellarcomplex may incorporate a simulated patella, a simulated patellar tendonand may additionally incorporate a simulated tibial tubercle. Thepatellar complex may be made of a material harder than the skin and thecapsule, for example a harder plastics material such as polyurethane.The patellar complex may allow removal of a part thereof to simulate abone-tendon-bone graft. The patellar complex may additionally beembedded in the penetrable packing material. The male mould mayincorporate recesses conforming to the anatomy of the femoral condyleswith the femoral notch therebetween. The male mould may additionallyincorporate recesses conforming to one or more of the anatomy of thearticular surface of the patella, plicae, the pes anserinus tendon andthe fat pad. The coating material may be applied separately to therecesses of the male mould.

The closure for the capsule may comprise an assembly simulating theanatomical features of the medial and lateral menisci, the anterior andposterior cruciate ligaments and the tibial articular surfaces. Theassembly may comprise first and second sub-assemblies with the medialand lateral menisci being formed as a first sub-assembly together withthe posterior cruciate ligament, and with the tibial articular surfacesbeing formed as a second sub-assembly together with the anteriorcruciate ligament. The sub-assemblies may be interconnected by means ofa skirt provided on the first sub-assembly and adapted to extend aroundthe periphery of the second sub-assembly. Additionally, the secondsub-assembly may be provided with a recess which receives the posteriorcruciate ligament of the first sub-assembly.

The method may include the step of securing the free ends of theposterior and anterior cruciate ligaments within the femoral notch. Thismay be effected by providing an elongate member extending from the freeend of each ligament and by passing the elongate member of one ligamentthrough opposite sides of the femoral notch. The elongate member maythen be secured externally of the capsule.

As an alternative, the joint comprising the surgical model may be in theform of a shoulder structure, the shoulder structure comprising ahumeral head, an articular surface of the glenoid process, a glenoidlabrum and a biceps tendon. The method may include the step of arrangingwithin the mould a simulated scapulo-clavicular complex positionedintermediate at least a part of the capsule and the skin. Thescapulo-clavicular complex may incorporate a portion of a simulatedclavicle and a portion of a simulated scapula, for example including theacromial and coracoid processes. The scapulo-clavicular complex may bemade of a harder material than the skin and the capsule, for example aharder plastics material such as polyurethane.

The male mould may incorporate recesses conforming to the anatomy of thehumeral head and the glenoid labrum. The male mould may additionallyincorporate recesses conforming to the anatomy of one or more of thelateral end of the clavicle and/or the lateral portion of the acromialprocess and/or one or more of the claviculo-acromial ligament, thecoraco-acromial ligament, the superior and/or middle gleno-humeralligaments, all or part of the inferior gleno-humeral complex such as oneor more of the anterior, axillary and posterior bands, the tendons ofthe supra spinatus, the infra spinatus and the teres minor muscles mayalso be formed in the capsule wall, together, optionally, with thesub-scapularis tendon.

The closure for the capsule may simulate the anatomical features of theglenoid process.

The method may include the step of securing a simulated biceps tendon inor externally on opposing walls of the capsule, for example behind thehumeral head and above the glenoid labrum.

The capsule may be manufactured as two or more capsule structures.Adjacent capsule structures may be interconnected by means of anaperture.

According to another aspect of the invention there is provided asurgical model in the form of a shoulder structure simulating certainaspects of the natural anatomical joint, the model comprising apenetrable outer skin, an impermeable penetrable capsule within themodel, and penetrable packing material around the capsule, wherein thecapsule conforms internally to the general anatomy of the internalcavity of the shoulder and contains simulated joint componentscomprising a humeral head, an articular surface of the glenoid process,a glenoid labrum and a biceps tendon.

The model may be provided with a generally flat base or may beconfigured to be received in a cradle, which cradle is provided with agenerally flat base. The base of the model or the cradle may be formedwith at least one recess for engaging with a complementary protrusionformed on a receiving tray.

The model may include a simulated scapulo-clavicular complexintermediate the capsule and the skin. Penetrable packing material maybe provided around at least a part of the simulated scapulo-clavicularcomplex. The scapulo-clavicular complex may incorporate a portion of asimulated clavicle and a portion of a simulated scapula, for exampleincluding the acromial and coracoid processes. The scapulo-clavicularcomplex may be made of a harder material than the skin and the capsule,for example a harder plastics material such as polyurethane.

The components simulating the humeral head and the glenoid labrum may beformed integrally with the capsule, for example they may be formed inthe capsule wall.

Components simulating the lateral end of the clavicle and/or the lateralportion of the acromial process may be formed in the capsule wall.Components simulating one or more of the claviculo-acromial ligament,the coraco-acromial ligament, the superior and/or middle gleno-humeralligaments, all or part of the inferior gleno-humeral complex such as oneor more of the anterior, axillary and posterior bands, the tendons ofthe supra spinatus, the infra spinatus and the teres minor muscles mayalso be formed in the capsule wall, together, optionally, with thesub-scapularis tendon.

The component simulating the glenoid process may be formed as a separateassembly to the remainder of the capsule. For example, the component maybe secured in an aperture formed in the capsule wall.

The biceps tendon may be secured in or externally on opposing walls ofthe capsule behind the humeral head and above the glenoid labrum.

The capsule may comprise two capsule structures. The capsule structuresmay be interconnected by means of an aperture which may simulate a tearin the tissue intermediate the two capsule structures.

Various pathologies can be simulated. For example, capsular tears androtator cuff tears can be formed, such as the aperture intermediate thecapsule structures. Alternative tears can allow the surgeon to practisesuturing or stapling, or even stapling part of the rotator cuff to abone in addition to suturing. Other pathologies may be simulated forexample by cutting the glenoid labrum to simulate a Bankart lesion.

The capsule may be filled with fluid such as water or saline, tosimulate synovial fluid, which fluid may be pressurised, to simulate theconditions under which the appropriate arthroscopic technique wouldusually be conducted.

The skin of the model and the capsule may be formed of an elastomericmaterial such as rubber, for example silicone rubber, or a colloidmaterial, for example based on gelatine.

The packing material may comprise light discrete particulate materialsuch as polystyrene beads or may comprise a moulded light material, forexample expanded polystyrene or polyurethane, or may comprise the samematerial as the skin and/or the capsule.

The capsule and/or the skin may incorporate, or may be at least partlysurrounded internally of the model by, a reinforcing material, such as afibrous, mesh or gauze material.

For a better understanding of the present invention and to show moreclearly how it may be carried into effect reference will now be made, byway of example, to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a male mould for use in themanufacture of a capsule for use in a model in the form of a knee jointmade by the method according to the present invention;

FIG. 2 is an exploded perspective view of an assembly for a closure foruse with a capsule manufactured using the male mould of FIG. 1;

FIG. 3 is a perspective view of a closure incorporating the assembly ofFIG. 2;

FIG. 4 is a cross-sectional view of one embodiment of a knee joint madeby the method according to the present invention;

FIG. 5 is a cross-sectional view of a first male mould for use in themanufacture of a first pouch part for use in a model in the form of ashoulder joint made by the method according to the present invention;

FIG. 6 is a cross-sectional view of a second male mould for use in themanufacture of a second pouch part for use in a model in the form of ashoulder joint made by the method according to the present invention;

FIG. 7 is a side elevational view of a closure for use with a pouch partmanufactured using the male mould of FIG. 6;

FIG. 8 is a cross-sectional view of a pouch incorporating pouch partsmade with the male moulds of FIGS. 5 and 6;

FIG. 9 is a cross-sectional view of a capsule incorporating the pouch ofFIG. 8 and the closure of FIG. 7;

FIGS. 10 and 11 illustrate a simulated bone structure in the form of ascapulo-clavicular complex;

FIG. 12 is a cross-sectional view of one embodiment of a shoulder jointmade by the method according to the present invention;

FIG. 13 is a cross-sectional view of part of the capsule shown in FIG.9;

FIG. 14 is a cross-sectional view of another part of the capsule shownin FIG. 9; and

FIG. 15 is a cross-sectional view of a further part of the capsule shownin FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

The model knee joint is manufactured by first providing a male mould 1corresponding to the configuration of the internal cavity of the kneewhen expanded by fluid under pressure. The male mould 1 incorporatesrecesses 3 conforming to the anatomy of the femoral condyles togetherwith recesses 5, 7 and 9, respectively, conforming to the anatomy of thefat pad, together with the articular surface of the patella, plicae andthe pes anserinus tendon (not shown). The mould 1 is supported at thelower end thereof.

Elastomeric moulding material is applied in an appropriate colour and ina thin layer to the recesses of the male mould 1. The moulding materialmay be a rubber, for example silicone rubber, or a colloid material,such as one based on gelatine. Silicone rubber material has theadvantage of a long shelf-life, but it is not bio-degradable. Colloidmaterial has the advantage that it is bio-degradable. Both siliconerubber and colloid material enable the surgeon to practise techniques ina realistic manner.

Thus, when a silicone rubber is used, the recess corresponding to thefat pad may be coated with silicone rubber coloured yellow, while therecesses corresponding to the articular surface of the patella, plicaeand the pes anserinus tendon may be coated with silicone rubber colouredwhite. If desired, fibrous material coloured red may be applied to thesurface of the mould to simulate blood vessels in the internal surfaceof the coating. Additionally, the region of the mould corresponding tothe femoral condyles may also be coated with silicone rubber colouredwhite. The remainder of the mould may then be coated with suitablycoloured silicone rubber. If desired, the recesses in the surface of thecoating, arising from the recesses of the mould, may be filled withsilicone rubber.

The moulding material is elastomeric and, when dry, can be removed fromthe male mould 1 simply by peeling the silicone rubber or colloidmaterial away from the mould, giving rise to a “pouch” which is open atits lower end, but which incorporates therewithin the anatomicalfeatures of inter alia the femoral condyles and the supra-patellarpouch.

The thickness of the coating may be selected such that the coating isgenerally self-supporting when removed from the male mould 1. Ifdesired, the coating may be reinforced with a fibrous, mesh or gauzematerial which may be incorporated into the coating or may be applied aspart of a further coating either to the pouch or, at a later stage, tothe entire capsule.

The configuration of the pouch is clear from FIGS. 1 and 4 as will beexplained in more detail hereinafter.

The lower end of the pouch is closed by a closure assembly 11 shown inFIGS. 2 and 3. The closure assembly 11 reproduces the anatomicalfeatures of the medial and lateral menisci 13 and 15 respectively,anterior and posterior cruciate ligaments 17 and 19 respectively andthe. tibial articular surfaces 21. This assembly is shown in explodedform in FIG. 2 and, in assembled form, in FIG. 3.

The assembly 11 is in two parts, an upper sub-assembly 23 and a lowersub-assembly 25. The upper sub-assembly 23 reproduces the medial andlateral menisci 13 and 15 respectively, together with the posteriorcruciate ligament 19, while the lower sub-assembly 25 reproduces thetibial articular surfaces 21, together with the anterior cruciateligament 17. The anterior cruciate ligament 17 of the lower sub-assembly25 is received in a recess formed between the menisci of the uppersub-assembly 23 and the menisci are provided with a depending peripheralskirt 27 which extends around the lower sub-assembly so that the twosub-assemblies are locked together to form the closure assembly 11. Itshould be noted that the upper sub-assembly could alternatively.incorporate the anterior cruciate ligament, with the lower sub-assemblyincorporating the posterior cruciate ligament. Strings 29 or the likeare attached by any suitable adhesive to the free ends of the cruciateligaments 17, 19 for reasons that will be explained in more detailhereinafter. It will be noted that it is not essential for the strings29 to be secured to the free ends of the cruciate ligaments and it maybe possible to provide strings passing within the ligaments. However, itis desirable for the ligaments to retain their resilient properties.

The closure assembly 11 is then inserted into the open lower end of thepouch and the strings 29 are each threaded on a needle (not shown) whichis inserted through the wall of the pouch, one at each side of thecondylar notch to simulate the anatomical arrangement of the ligaments.In this way, the proximal ends of the ligaments are secured within thefemoral notch in an anatomically realistic manner, for example inrecesses provided therein.

The strings 29 are secured outside the pouch, for example by means of aknot and/or with an adhesive, silicone rubber or colloid material, andany excess string is removed. The closure assembly 11 is then secured inposition with an adhesive, silicone rubber, colloid material or the liketo form a watertight capsule 31 which conforms internally to the anatomyof the internal cavity of the knee when expanded by fluid underpressure. As noted above, the capsule may be reinforced with a fibrous,mesh or gauze material which may be applied as part of a coating to theentire capsule.

In a separate stage (not illustrated) a mould, conforming to theexternal shape of the model knee joint of FIG. 4 is provided with theknee inverted and is coated internally with a material to form a skin 32for the model. As an alternative to coating, a separate skin 32 may beapplied to the internal surface of the mould. For example, the materialmay comprise a silicone rubber or colloid material which is ideallycoloured to simulate skin. If desired, the skin may be reinforced with afibrous material. A patellar complex 33 is then positioned within themould in the appropriate position and the capsule 31 is positioned abovethe patellar complex.

The patellar complex 33 incorporates the patella 37 (other than thearticular surface 35 thereof which has previously been formed as part ofthe capsule), the patellar tendon 39 and a tibial tubercle 41. Thepatellar complex 33 is made of a harder material than the material ofthe skin, for example a harder plastics material such as polyurethane,in order to give a realistic impression to the surgeon when examining(palpating) the model prior to commencing an operation.

With the patellar articular surface appropriately positioned relative tothe patella, the patellar complex 33 can be secured in position, ifdesired, for example with an adhesive, silicone rubber or colloidmaterial. Packing material 43 may be positioned around the capsule andthe upper part of the mould closed with silicone rubber or colloidmaterial.

The packing material 43 may be a lightweight material such aspolystyrene beads or expanded polystyrene or polyurethane block, but mayalternatively be the same material as that of the skin 32, i.e. siliconerubber or colloid material.

Alternatively, the mould may be filled with silicone rubber or colloidmaterial.

A recess 45 may be formed in the base by any suitable means, such as bymoulding the recess into the base or by subsequently removing materialto form the recess.

The capsule 31 may be filled with a fluid such as water or saline, tosimulate synovial fluid, and the fluid may be pressurised to simulatethe conditions under which the appropriate arthroscopic technique wouldusually be conducted.

Various pathologies can be simulated. For example, material may bedeposited in para-condylar gutters which extend below and to the side ofthe menisci to simulate a pathological loose body. Other pathologies maybe simulated by cutting a joint surface to leave a loose chondral flap,abrading a joint surface to leave exposed bone, a ligament and/or one ormore menisci may be torn to simulate injury. Additionally, the patellarcomplex may be made in a number of components to allow removal of partof the complex to simulate a bone-tendon-bone graft.

Thus the model is primarily concerned with the internal shape of theknee joint and not with other anatomical features, such as the shafts ofbones, which are not visible through an arthroscope. However, theinternal anatomy of the capsule is very realistic. The capsule, and themodel, are watertight and pressure resistant and therefore allowrealistic simulation of true operating conditions. Additionally, themodel permits a surgeon to practise other procedures such as suturing ofa meniscus, while the presence of the pes anserinus tendon gives thesurgeon additional indications as to the location of the instrumentswithin the model.

The model shoulder joint is manufactured by providing two male moulds101 and 103 as shown in FIGS. 5 and 6, although a single male mouldcould be employed if desired. The male moulds 101 and 103 correspond tothe configuration of the internal cavities of the shoulder when expandedby fluid under pressure. The male mould 101 simulates the sub-acromialspace (or bursa) within the shoulder and the male mould 103 simulatesthe glenohumeral space.

The male mould 101 incorporates recesses (not shown) in the uppersurface thereof conforming to the anatomy of the lateral end of theclavicle and to the lateral portion of the acromial process of thescapula. Recesses are also formed conforming to the anatomy of theclaviculo-acromial ligament and the coraco-acromial ligament. The mould101 is supported at the lower end thereof.

The male mould 103 incorporates a recess 105 in the upper part thereofconforming to the anatomy of the humeral head and a generally ovalrecess 107 in the lower part thereof conforming to the anatomy of theglenoid labrum.

The exterior surface of the male mould 103 is formed with a number ofelongate protrusions (not shown) representing the several ligaments thatspan the joint and make up the support for the shoulder. The variousligaments envelope the humeral head and include the superior and middlegleno-humeral ligaments which extend generally in a series of arcs fromthe anterior surface of the glenoid fossa of the glenoid process to theanterior aspect of the humeral head, the inferior gleno-humeral complexwhich extends in a hammock-like structure around the left-hand side ofthe mould 103 (as shown in the figure) and cradles the humeral head andcomprises. the anterior, axillary and posterior bands, and a cuff ofmusculo-tendinous structures known as the rotator cuff, including thetendons of the supra spinatus, infra spinatus and teres minor muscleswhich extend from the posterior side of the glenoid fossa to theposterior aspect of the humeral head. As many of these ligaments as aredesired may be defined as recesses on the external surface of the mould103. Additionally, the sub-scapularis tendon may be defined intermediatethe superior and middle gleno-humeral ligaments.

Elastomeric moulding material is applied in an appropriate colour and ina thin layer to the recesses of each of the male moulds 101 and 103. Aswith the model knee joint, the moulding material may be a rubber, forexample silicone rubber, or a colloid material, such as one based ongelatine.

Thus, when a silicone rubber is used, the recesses in the male moulds101 and 103 corresponding to the clavicle, the acromial process, thecoracoid process and the humeral head may be coated with silicone rubbercoloured white, while the recesses corresponding to the variousligaments may be coated with silicone rubber coloured white or any othersuitable colour. If desired, fibrous material coloured red may beapplied to the surface of one or more of the moulds to simulate bloodvessels in the internal surface of the coating. The remainder of each ofthe moulds may then be coated with suitably coloured silicone rubber. Ifdesired, the recesses in the surface of the coating, arising from therecesses of the moulds, may be filled with silicone rubber.

The moulding material is elastomeric and, when dry, can be removed fromeach of the male moulds 101 and 103 simply by peeling the siliconerubber or colloid material away from the respective mould giving rise toa “pouch” which is open at its side, but which incorporates therewithinthe desired anatomical features.

The thickness of the coating may be selected such that the coating isgenerally self-supporting when removed from the mould. If desired, thecoating may be reinforced with a fibrous, mesh or gauze material whichmay be incorporated into the coating or may be applied as part of afurther coating either to the pouch or, at a later stage, to the entirecapsule.

In the illustration of the method, the pouch is made in two parts 109and 111 which are subsequently interconnected by way of an aperture 113formed in each part, the two parts being secured together with-the aidof silicone rubber, colloid material or other suitable adhesive.

After they have been interconnected, the two pouch parts 109 and 111communicate with one another by way of the aperture 113 which simulatesa tear in the tissue between the two pouch parts. The combined pouch isshown in cross-section in FIG. 8.

As an alternative, the pouch may be made in a single component.

A component 115, for example of silicone rubber or colloid material,with or without a string passing therethrough, representing the bicepstendon is threaded through the side walls of the pouch part 111 with theaid of a needle (not shown) so as to pass over the humeral head and issecured to the exterior of the pouch, for example with silicone rubber,colloid material or any suitable adhesive. The component 115representing the biceps tendon is shown in FIG. 9 as extending acrossthe superior surface of the humeral head and secured in opposing wallsof the pouch behind the humeral head and above the glenoid labrum.

The pouch is closed by a closure member 117 as shown in FIGS. 7 and 9.The closure member 117 reproduces the anatomical features of thearticular surface of the glenoid process. The closure member 117 issecured in position with an adhesive, silicone rubber, colloid materialor the like to form a watertight capsule 119 as shown in FIG. 9, whichwatertight capsule conforms internally to two of the internal cavitiesof the shoulder when expanded by fluid under pressure. As noted above,the capsule. 119 may be reinforced with a fibrous, mesh or gauzematerial which may be applied as part of a coating to the entirecapsule.

Various pathologies can be simulated. For example, capsular tears androtator cuff tears, such as the aperture shown between the capsulecomponents. Alternative tears can allow the surgeon to practise suturingor stapling, or even stapling part of the rotator cuff to a bone inaddition to suturing. Other pathologies may be simulated for example bycutting the glenoid labrum to simulate a Bankart lesion.

The capsule 119 may be filled with a fluid such as water or saline, tosimulate synovial fluid, and the fluid may be pressurised to simulatethe conditions under which the appropriate arthroscopic technique wouldusually be conducted.

In a separate stage, a scapulo-clavicular complex 121 which simulatespart of the bone structure of the shoulder is moulded in the form shownin FIGS. 10 and 11. The scapulo-clavicular complex 121 comprises theanatomy of part of the clavicle 123 integrally formed with part of thescapula 125, in particular the acromial process 127, with thesub-acromial space therebeneath, and the coracoid process 129. Thescapulo-clavicular complex 121 is made of a harder material than thecapsule and may be made, for example a harder plastics material such aspolyurethane, in order to give a realistic impression to the surgeonwhen examining (palpating) the model prior to commencing an operation.

Part of the capsule 119 is positioned intermediate thescapulo-clavicular complex 121 with the clavicular protrusion and theacromial protrusion within the capsule being positioned adjacent thecorresponding components of the scapulo-clavicular complex. In this way,the scapulo-clavicular complex 121 provides a degree of support for thecapsule 119. However, if desired, the scapulo-clavicular complex 121 canbe extended to provide additional support for the capsule 119.

In a further separate stage a mould, conforming to the external shape ofthe model shoulder joint of FIG. 12 is provided with the shoulderinverted and is coated internally with a material to form a skin 131 forthe model. As an alternative to coating, a separate skin 131 may beapplied to the internal surface of the mould. For example, the materialmay comprise a silicone rubber or colloid material which ideally iscoloured to simulate skin. If desired, the skin may be reinforced with afibrous material. The capsule 119, positioned within thescapulo-clavicular complex 121 in the required orientation, is locatedwithin the mould in the appropriate position close to the skin surfaceto simulate the anatomical position of the bones and secured inposition, if desired, for example with an adhesive, silicone rubber orcolloid material. Packing material 133 may be positioned around thecapsule 119 and the upper part of the mould closed with silicone rubberor colloid material. Alternatively, the mould may be filled withsilicone rubber or colloid material. Recesses 135 and 137 may be formedin the model by any suitable means, such as by moulding the recess intothe base or by subsequently removing material to form the recess.

The packing material 133 may be a lightweight material such aspolystyrene beads or expanded polystyrene or polyurethane block, but mayalternatively be the same material as that of the skin, i.e. siliconerubber or colloid material.

The resulting model resembles in external appearance a right humanshoulder joint with the arm abducted 45° from the patient's side and 45°forward. The model has two generally flat bases, either of which can bepositioned in use on a tray (not shown), with the recess 135 or 137engaging a complementary protrusion provided on the tray.

Recess 135 allows simulation of a semi-reclining or “beach-chair”position, while recess 137 allows simulation of a patient lying on hisside.

As noted previously, the watertight capsule 119 comprises two parts, orcapsule structures, 109 and 111, one part 109 being positionedintermediate the scapulo-clavicular complex 121. The capsule structure109 simulates the sub-acromial space (or bursa) within the shoulder andthe capsule structure 111 simulates the gleno-humeral space.

The upper internal surface (or roof) of the capsule structure 109 isshown in more detail in FIG. 13. The upper internal surface is formedwith a clavicular protrusion 139 conforming to the lateral end of theclavicle and with an acromial protrusion 141 conforming to the lateralportion of the acromial process of the scapula. Protrusions are alsoformed conforming to the anatomy of the claviculo-acromial ligament 143and the coraco-acromial ligament 145.

The capsule structure 111 is shown in more detail in FIGS. 14 and 15.FIG. 14 is taken in the direction looking to the right in FIG. 9, whileFIG. 15 is taken in the direction looking left in FIG. 9. As can be seenfrom FIGS. 9 and 14, the inner surface of the capsule is formed with agenerally oval protrusion 147 representing the glenoid labrum havingarranged therewithin a protrusion 149 representing the articular surfaceof the glenoid process.

As can be seen from FIGS. 9 and 15, the capsule structure 111 is formedwith an internal protrusion 151 conforming to the anatomy of the humeralhead, there being a space around the sides of the protrusion.

The internal surface of the capsule structure 111 is formed with anumber of elongate protrusions representing the several ligaments thatspan the joint and make up the support for the shoulder. The variousligaments envelope the humeral head 151 and include the superior andmiddle gleno-humeral ligaments which extend generally in a series ofarcs from the anterior surface of the glenoid fossa of the glenoidprocess as shown in FIG. 14 to the anterior aspect of the humeral headas shown in FIG. 15, the inferior gleno-humeral complex which extends ina hammock-like structure around the lower part of the capsule structure111 and cradles the humeral head and comprises the anterior, axillaryand posterior bands, and the rotator cuff, including the tendons of thesupra spinatus, infra spinatus and teres minor muscles which extend fromthe posterior side of the glenoid fossa to the posterior aspect of thehumeral head as shown in FIG. 14. As many of these ligaments as aredesired may be defined as ridges on the internal surface of the capsulestructure 111. Additionally, the sub-scapularis tendon may be definedintermediate the superior and middle gleno-humeral ligaments. FIGS. 14and 15 show in particular the superior and middle gleno-humeralligaments 153 and 155, respectively, the anterior and posterior bands157 and 159, respectively of the inferior gleno-humeral ligamentcomplex, and the infra-spinatus 161.

Thus the model is primarily concerned with the internal shape of theshoulder joint and not with other anatomical features, such as theshafts of bones, which are not visible through an arthroscope. However,the internal anatomy of the capsule is very realistic. The capsule, andthe model, are watertight and pressure resistant and therefore allowrealistic simulation of true operating conditions. Additionally, themodel permits a surgeon to practise other procedures such as suturing ofthe glenoid labrum.

What is claimed is:
 1. A method of manufacturing a surgical modelsimulating certain aspects a natural anatomical joint, the methodcomprising the steps of: providing a male mould (1, 101, 103) conformingexternally to the general anatomy of an internal cavity of the joint;applying a coating of resilient impermeable penetrable material over themale mould (1, 101, 103); removing the coating from the male mould toform an open capsule; providing a closure (11, 117) for the capsule andattaching the closure to the open capsule so as to form an impermeablepenetrable capsule (31, 119), the capsule conforming internally to thegeneral anatomy of the internal cavity of the joint and containingsimulated joint components; arranging the capsule with a second mould,the second mould being at least partly lined with a penetrable outerskin material (32, 131); embedding the capsule in a penetrable packingmaterial (43, 133); and removing the surgical model from the secondmould.
 2. A method according to claim 1 and including the step ofreinforcing the model.
 3. A method according to claim 2, wherein thereinforcing step comprises applying reinforcement to the coating ofresilient material.
 4. A method according to claim 1, wherein thecapsule (31, 119) is filled with fluid to simulate synovial fluid.
 5. Amethod according to claim 1, wherein the skin (32, 131) of the model andthe capsule (31, 119) are formed of a material selected from the groupconsisting of an elastomeric compound and a colloid material.
 6. Amethod according to claim 1, wherein the packing material (43, 133) isselected from the group consisting of light, discrete particulatematerial, a moulded light material, the same material as the skin (32,131), and the same material as the capsule (31, 119).
 7. A methodaccording to claim 1, wherein the closure (11, 117) for the capsule (31,119) comprises an articular surface (21, 149) of a bone forming part ofthe joint.
 8. A method according to claim 1, including the further stepof passing an elongate member (17, 19, 115) simulating at least one of aligament and a tendon through at least a part of the capsule (31, 119).9. A method according to claim 8, wherein the elongate member (17, 19,115) is secured externally of the capsule (31, 119).
 10. A methodaccording to claim 8, wherein the elongate member (17, 19, 115)comprises an elastomeric material.
 11. A method according to claim 8,wherein the elongate member (17, 19) incorporates a flexible elongateelement (29) extending from at least one end thereof.
 12. A methodaccording to claim 11, wherein the flexible elongate element (29)extends through the elongate member (17, 19) in the axial directionthereof.
 13. A method according to claim 11, wherein the flexibleelongate element (29) is selected from the group consisting of stringand a like filamentary material.
 14. A method according to claim 1,wherein the capsule (119) is manufactured as at least two capsulestructures (109, 111).
 15. A method according to claim 14, whereinadjacent capsule structures (109, 111) are interconnected by means of anaperture (113).
 16. A method according to claim 2, wherein the model isreinforced with a material selected from the group consisting offibrous, mesh and gauze material.
 17. A method according to claim 2,wherein the reinforcing step comprises applying reinforcement to theskin.
 18. A method according to claim 4, wherein the fluid filling thecapsule is selected from the class consisting of water and saline.
 19. Amethod according to claim 4, wherein the fluid filling the capsule ispressurised.
 20. A method according to claim 5, wherein the elastomericcompound is selected from the group consisting of rubber and siliconerubber.
 21. A method according to claim 5, wherein the colloid materialis based on gelatine.
 22. A method according to claim 6, wherein thelight, discrete particulate material comprises polystyrene beads.
 23. Amethod according to claim 6, wherein the moulded light material isselected from the group consisting of expanded polystyrene andpolyurethane.